criterion of falsifiability, in thephilosophy of science, a standard of evaluation of putatively scientific theories, according to which a theory is genuinely scientific only if it is possible in principle to establish that it is false. The British philosopherSir Karl Popper (1902–94) proposed thecriterion as a foundational method of theempirical sciences. He held that genuinely scientific theories are never finally confirmed, because disconfirming observations (observations that are inconsistent with the empirical predictions of the theory) are always possible no matter how many confirming observations have been made. Scientific theories are instead incrementallycorroborated through the absence of disconfirming evidence in a number of well-designed experiments. According to Popper, somedisciplines that have claimed scientific validity—e.g.,astrology,metaphysics,Marxism, andpsychoanalysis—are not empirical sciences, because their subject matter cannot be falsified in this manner.